Enhanced vehicle window anti-fogging strategy

ABSTRACT

A method for defogging a window of a vehicle includes steps of determining a risk of window fogging and automatically selecting a climate control system operating mode according to that determined risk of window fogging. The climate control system operating mode is selected from: an outside air mode, an air-conditioning mode, and a defrost mode. A controller determines the risk of window fogging according to one or more inputs, and the same or a different controller may automatically select the climate control system operating mode.

TECHNICAL FIELD

This disclosure relates generally to vehicle heating, ventilation, and air conditioning (HVAC) system operation. More particularly, the disclosure relates to strategies for activating suitable defogging/defrosting systems according to determined conditions, while maintaining suitable comfort levels for vehicle occupants.

BACKGROUND

A vehicle includes many systems and devices are devoted to maintaining passenger comfort. For example, modern automotive heating, ventilation, and air-conditioning (HVAC) systems are highly advanced, and include various manually and automatically operated features whose fundamental purpose is to preserve and enhance passenger comfort. Some modern vehicles include automated passenger comfort-related systems relying on sensor-driven coordination of actuation of the vehicle heating and/or cooling systems according to a variety of inputs such as ambient temperature, ambient humidity, passenger cabin temperature, passenger cabin humidity, sun load, and others.

Certain other vehicle systems are not typically designed with passenger comfort in mind. For example, multiple systems and strategies are known in the vehicle industry for preventing or eliminating vehicle window fogging/frosting. Some such systems are designed to anticipate and so prevent fogging/frosting, such as by using algorithms to determine a risk of window fogging/frosting and activating one or more window defog/defrost systems. Typically, these systems/strategies rely on simply directing a suitably heated and/or dehumidified airflow against the window to prevent or clear fogging/frosting. While effective for their intended purpose, conventional systems and strategies emphasize window defogging without any consideration of passenger comfort, since the priority is window defogging to provide an unimpeded view of the road. As an example, manual or automatic actuation of a window defogging system may direct a blast of dehumidified and/or heated air against a window that effectively clears any fog or frost therefrom. However, because the dehumidified and/or heated airflow is generated regardless of any consideration of ambient temperature/humidity, passenger cabin temperature/humidity, etc., passenger cabin occupant comfort may be negatively impacted.

To solve this and other problems, the present disclosure relates at a high level to systems and methods for vehicle window defogging which select a vehicle climate control system defogging strategy according to determined conditions, and/or which incrementally apply various vehicle climate control system defogging strategies and systems as necessary according to determined conditions and/or as conditions change. The systems and methods rely on various vehicle sensor and user-implemented inputs in determining a risk of window fogging created by particular conditions. By such incremental application of strategies/systems, a necessary level of vehicle window defogging is applied while preserving vehicle occupant comfort to the extent possible.

SUMMARY

In accordance with the purposes and benefits described herein, in one aspect of the disclosure a method for defogging a window of a vehicle is provided, comprising determining a risk of window fogging and automatically selecting a climate control system operating mode according to the determined risk of window fogging. The climate control system operating mode is selected from the group consisting of: an outside air mode, an air-conditioning mode, and a defrost mode. The risk of window fogging is determined by a controller according to one or more inputs. The climate control system operating mode may be automatically selected by the same or a different controller. The controller and/or the different controller comprising one or more processors may be associated with a vehicle climate control module (CCM).

In one possible embodiment, the controller or the different controller select a one of the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging. The controller or the different controller may increasing a climate control system blower speed to increase a rate of airflow provided by the selected one of the outside air mode, the air-conditioning mode, and the defrost mode if determined necessary according to the determined risk of window fogging. In another possible embodiment, the controller or the different controller sequentially actuate the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging. The controller or the different controller may implement intervening steps of increasing a climate control system blower speed to increase a rate of airflow provided by one or more of the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging are contemplated.

In embodiments, the inputs by which the controller determines the risk of window fogging may be provided respectively by the group consisting of a windscreen relative humidity sensor, a vehicle-associated exterior ambient temperature sensor, a passenger cabin temperature sensor, a window wiper system mode sensor, and a window heated glass mode sensor.

In another aspect, a method for defogging a window of a vehicle is provided, comprising providing one or more inputs to a processor comprised in a vehicle climate control module (CCM). A risk of window fogging is determined by the processor according to the one or more inputs. According to the determined risk of window fogging, the same or a different processor automatically selects a climate control system operating mode from the group consisting of: an outside air mode, an air-conditioning mode, and a defrost mode.

In embodiments, the processor or the different processor may directly select a one of the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging, or may actuate the outside air mode, the air-conditioning mode, and the defrost mode sequentially. Intervening steps of increasing a climate control system blower speed to increase a rate of airflow provided by one or more of the outside air mode, the air-conditioning mode, and the defrost mode may be provided, implemented by the processor or the different processor. The inputs may be provided to the processor by the group of sensors consisting of a windscreen relative humidity sensor, a vehicle-associated exterior ambient temperature sensor, a passenger cabin temperature sensor, a window wiper system mode sensor, and a window heated glass mode sensor.

In yet another aspect, a window defogging system for a vehicle is provided, comprising one or more processors comprised in a vehicle climate control module (CCM) and configured to determine a risk of window fogging according to one or more received inputs. The system further includes one or more sensors adapted to send the one or more inputs to the one or more processors and a climate control system operatively connected to the one or more processors. The one or more processors are further configured to actuate the climate control system in one or more of an outside air mode, an air-conditioning mode, and a defrost mode according to the determined risk of window fogging.

In embodiments, the one or more processors are configured to directly select a one of the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging. In alternative embodiments, the one or more processors are configured to sequentially actuate the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging. The one or more processors may be further configured to increase a climate control system blower speed to increase a rate of airflow provided in one or more of the outside air mode, the air-conditioning mode, and the defrost mode before advancing to a next climate control system window defog system operating mode. In embodiments, the one or more sensors are selected from the group consisting of a windscreen relative humidity sensor, a vehicle-associated exterior ambient temperature sensor, a passenger cabin temperature sensor, a window wiper system mode sensor, and a window heated glass mode sensor.

In the following description, there are shown and described embodiments of the disclosed vehicle window defogging methods and systems. As it should be realized, the systems/methods are capable of other, different embodiments and their several details are capable of modification in various, obvious aspects all without departing from the systems and methods as set forth and described in the following claims. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures incorporated herein and forming a part of the specification, illustrate several aspects of the disclosed vehicle window defogging methods and systems, and together with the description serve to explain certain principles thereof. In the drawings:

FIG. 1 schematically depicts a method for operating a window defogging system according to the present disclosure;

FIG. 2 illustrates a vehicle including a window defogging system for implementing the method of FIG. 1;

FIG. 3 illustrates various operating modes of a vehicle HVAC system for implementing the method of FIG. 1;

FIG. 4 shows in schematic form a system for determining a probability of window fogging; and

FIG. 5 shows a representative look-up table array for the system of FIG. 4.

Reference will now be made in detail to embodiments of the disclosed vehicle window defogging methods and systems, examples of which are illustrated in the accompanying drawing figures wherein like reference numerals identify like features.

DETAILED DESCRIPTION

The present disclosure is directed to methods for systematically responding to a risk of window fogging by incrementally increasing a response provided by a window defogging system, and to vehicle systems configured to implement the described methods. In particular, as shown schematically in FIG. 1, at a high level a method 100 for operating a vehicle window defogging system contemplates a vehicle window defogging system which responds to a determined risk of window fogging by actuating a vehicle climate control system outside air operating mode to introduce an outside air airflow against the window interior (step 102) and by increasing a climate control system blower speed to increase a rate of the outside air airflow (step 104). As will be appreciated, the term “outside air airflow” refers to routing exterior air, i.e. fresh/ambient air, from an exterior of the vehicle to the vehicle passenger cabin by various known systems and devices.

The window defogging system then actuates an air-conditioning (AC) operating mode of the vehicle climate control system air-conditioning operating mode by engaging a vehicle AC compressor (step 106 a) and lowering an AC evaporator temperature (step 106 b). As will be appreciated, this causes dehumidification of the outside air airflow initiated in steps 102/104. Finally, the window defogging system actuates a defrost operating mode of the vehicle climate control system engaging a defrost air distribution mode to direct the dehumidified outside air airflow against the window interior (step 108), and by increasing the climate control system blower speed to increase a rate of the dehumidified outside air airflow against the window interior (step 110).

This process may be considered as calculating an Enhanced Windshield Anti-Fogging Strategy (EWAFS) airflow adder to be implemented on top of an existing HVAC setting previously determined automatically for passenger comfort. For example, if the HVAC is set on AUTO, the calculated EWAFS airflow adder will be added to the automatically determined climate control system blower speed. On the other hand, if a user has overridden to a manual climate control system blower setting, the EWAFs airflow adder will not be included.

As will be appreciated, the vehicle window defogging system may proceed sequentially through each of the above-listed steps each time the system is actuated. However, in embodiments the window defogging system may only proceed through the listed steps to the extent necessary to stabilize or decrease the risk of fogging, which in one non-limiting example could be interpreted by the system as humidity values stabilizing or decreasing. So, for example, if introducing the outside air airflow against the window interior (step 102) and increasing the climate control system blower speed to increase the rate of the outside air airflow (step 104) sufficiently stabilizes or decreases the risk of fogging, the window defogging system will not proceed to step 106.

It will also be appreciated that the steps of increasing the climate control system blower speed (steps 104 and 110) may be limited according to blower and/or vehicle specifications. For example, current vehicle software may only allow a maximum blower speed increase of 2 volts in the event of an increased risk of fogging. Of course, the skilled artisan understands that this value is calibratable, and may vary according to vehicle make and model.

FIG. 2 schematically illustrates elements of a representative window defogging system suitable for implementing the method 100. A vehicle 200 includes a climate control system, i.e. HVAC system 202. The elements of a vehicle HVAC system are well-known in the art, and do not require extensive discussion herein, but typically include at least an air-conditioning (AC) system 204 comprising a compressor, a condenser, an expansion valve, and an evaporator. A heating system 206 is also included, comprising at least a heater core. A blower 208 controls a rate of airflow of heated, cooled, and or outside air entering a passenger cabin 210 of the vehicle. An airflow regulating door system 212 comprises a series of doors/valves and actuators controlling the path of airflow of heated, cooled, and or outside air through various HVAC ducts (not shown) and entering the passenger cabin 210 via one or more vents. The vents may include dash panel 214-mounted vents such as a defrost vent 216 oriented to direct airflow against an interior surface of the windshield 218, dash panel-mounted vents 220 oriented to direct airflow towards a passenger cabin 210 occupant, floor vents 221, and others.

The vehicle 200 may further include other systems designed to prevent or remove window fogging/frosting, such as a windshield wiper system 222 including wiper blades 223 and a wiper motor 225. The vehicle 200 may further include a heated backlight (rear window) system 224. As is known, the heated backlight system 224 may include a heat source 226, for example embedded heating elements embedded in the material of the backlight, an infrared heat source for heating the backlight, and others.

A controller 228, which in an embodiment may be one or more processors 230 associated with a climate control module (CCM) 232, is provided in operative communication with the HVAC system 202. The controller 228 is further in communication by wired or wireless means with an array of sensors, each configured to emit inputs which are received by the controller 228. In one possible embodiment, the array of sensors may include one or more of a windshield humidity sensor 234, an ambient (vehicle-exterior) temperature sensor 236, and a passenger cabin temperature sensor 238. Of course, inclusion of other sensors is contemplated, for example vehicle occupancy sensors (not shown in this view but which, as is known, may be as simple as seat-mounted pressure or capacitance switches or as complex as proximity sensors, infrared sensors, camera systems, and others), sun load sensors (not shown) of known design, and others. One or more control panels or actuators 240 may be provided whereby a user may control elements of the HVAC system 202, the windshield wiper system 222, the heated backlight 224, and others. The control panels or actuators 240 may further be in communication with the controller 228, or with a different controller which is in turn in communication with the controller 228.

One or more inputs from the above-described sensors that are indicative of environmental conditions that may be conducive to window fogging are provided to the controller 228, and from those inputs a risk of window fogging is determined. A number of possible methods of and associated algorithms for determining a risk of window fogging by way of a controller 228 are known, and are contemplated for use herein. For example, the controller 228/processors 230 may be configured to receive inputs from the windshield humidity sensor 234 and to compare those with a threshold windshield relative humidity level predetermined to pose a risk of window fogging. Alternatively, inputs of multiple measured conditions such as windshield relative humidity, ambient temperature, and passenger cabin temperature provided respectively by the windshield humidity sensor 234, the ambient temperature sensor 236, and the passenger cabin temperature sensor 238 may be received by the controller 228/processors 230. A suitable window fogging risk algorithm may then be applied by the controller 228/processors 230 to determine a risk of window fogging according to the measured conditions. In one possible embodiment, the fogging risk algorithm provided in U.S. Pat. No. 6,155,061 to Ford Motor Company for Method of Determining Windshield Fogging Based on Inference from Presence of Rain, the contents of which are incorporated herein by reference, may be used. Of course, other fogging risk algorithms are known and contemplated for use herein.

Alternatively or additionally, risk of window fogging may be determined by non-sensor inputs provided automatically or according to actions taken by vehicle occupants. For example, use of control panel 240 to actuate the windshield wiper system 222 may be interpreted by the controller 228/processors 230 as an indicator of imminent or actual window fogging. Equally, actuation of a heated windshield mode comprising direction of a heated airflow against an interior surface of windshield 218 via defrost vent 216 may be interpreted by the controller 228/processors 230 as an indicator of imminent or actual window fogging. Likewise, use of control panel 240 to actuate the heated backlight system 224 may be interpreted by the controller 228/processors 230 as an indicator of imminent or actual window fogging.

Once a risk of window fogging has been determined by the controller 228/processors 230, the method summarized above and shown in FIG. 1 is implemented. In one possible embodiment it is contemplated to implement the method of FIG. 1 at one or more of various post-startup phases of operation of vehicle 200. In a representative implementation shown in FIG. 3, three phases of operation of an HVAC system 202 as depicted in FIG. 2 are illustrated. These include an evaporator purge phase 300, a cold engine lock-out (CELO) phase 302, and an automatic mode determination phase 304. The phases 300, 302, 304 are shown along an x-axis illustrating a representative timeline for phases 300, 302, 304.

In evaporator purge phase 300, the HVAC system 202 is placed in a floor mode 306 and the blower 208 is operated at an initial speed, in the depicted embodiment being 4.2 volts. This phase is implemented for approximately 3 seconds.

Next, in CELO phase 302 the HVAC system 202 is placed in a windshield mode 308 and the blower 208 is operated at a CELO limited rate of 4 volts. This phase may continue for a predetermined time period, for example 3-5 minutes. Alternatively, the CELO phase 302 may continue until a suitable temperature sensor determines that an engine coolant temperature has reached a predetermined threshold, for example 50° C. If, at this stage, a user-initiated input 310 is detected such as use of control panel 240 to actuate the windshield wiper system 222, to actuate the heated windshield mode as described above, or to actuate the heated backlight system 224, as described above this may be interpreted by the controller 228/processors 230 as an indicator of imminent or actual window fogging. The controller 228/processors 230 then implement the EWAFS airflow adder 312 as described above, and increase the blower 208 speed from the base 4 volts as needed. As noted above, the skilled artisan will appreciate that the blower 208 speed increase may be limited according to blower and/or vehicle specifications. For example, current vehicle software may only allow a maximum blower speed increase of 2 volts in the event of an increased risk of fogging. Of course, the skilled artisan understands also that this value is calibratable, and may vary according to vehicle make and model.

Once the CELO phase 302 has terminated, the automatic mode determination phase 304 may initiate. In this phase, it is presumed that the HVAC system 202 is set to a desired comfort level, either automatically or by vehicle 200 occupant action. In the automatic mode determination phase 304, a mode determination process 314 is implemented to determine whether an EWAFS airflow adder 312 should be implemented. At step 316, the controller 228/processors 230 determine whether a user-initiated input 310 is detected such as use of control panel 240 to actuate the windshield wiper system 222, to actuate the heated windshield mode as described above, or to actuate the heated backlight system 224 as an indicator of imminent or actual window fogging. If not, at step 318 the controller 228/processors 230 determine whether the ambient temperature is at or below a threshold temperature (in one non-limiting example 5° C.) by way of inputs from the ambient temperature sensor 236. If not, at step 320 the HVAC system 202 is placed in floor mode.

If the controller 228/processors 230 determine that a user-initiated input 310 has been received, at step 322 the HVAC system 202 is placed in a calibratable mode for a predetermined time period, for example 2 minutes until after the controller 228/processors 230 receive an input indicating that the windshield wiper system 222, heated windshield mode, or heated backlight system 224 have been discontinued. The controller 228/processors 230 then return to step 318 to determine whether the ambient temperature is at or below the threshold temperature by way of inputs from the ambient temperature sensor 236. If so, the controller 228/processors 230 then at step 324 determine a risk of window fogging. In one possible embodiment, the determination of risk of window fogging may be made by reference to a lookup table 326 of window fogging probability versus HVAC system 202 mode. Alternatively, the determination could be made according to an active calculation via a suitable algorithm by the controller 228/processors 230.

If a risk of window fogging is determined, the blower 208 is set at a speed/airflow rate 328 comprising a comfort based calculation plus the EWAFS airflow adder 312 as described above. In this manner, vehicle 200 passenger comfort is maintained to the extent possible, while reducing or eliminating a risk of window fogging according to either vehicle occupant manual inputs, determination of environmental conditions, or both.

Obvious modifications and variations are possible in light of the above teachings. For example, alternative systems/methods for calculating a risk of window fogging to implement of the above-described systems and methods are possible and contemplated. In one such possible alternative embodiment, FIG. 4 shows in schematic form a system 400 for the determination of probability of fog on the interior surface of the windshield 218 or other interior glass. The system 400 relies on inputs from the windshield humidity sensor 234 (measured in %) and the ambient (vehicle-exterior) temperature sensor 236 (see FIG. 2), from which the controller 228 calculates an initial estimate of probability of fogging. The system 400 may optionally provide a calculation of a rate of change of humidity over time to the controller 228, calculated by a proportional-integral-derivative (PID) controller 402 using the inputs from the windshield humidity sensor 234 and the ambient temperature sensor 236 and an internal or other timer 404.

The system 400 then uses various inputs whereby the controller 228 calculates modifiers for the initial estimate of fogging probability. In one possible embodiment, the system 400 may provide inputs indicative of blower 208 motor speed (measured in voltage or %) and HVAC system 202 airflow distribution mode (e.g. Panel mode, Floor mode, etc.), from which the controller 228 calculates an Airflow Modifier for the initial estimate of fogging probability. Inputs from vehicle occupancy sensors 235 (see FIG. 2) may be provided to allow the controller to calculate a vehicle Occupant Modifier. Inputs relative to the windshield wiper system 222 status (on/off/intermittent) may be used by the controller 228 to calculate a Wiper Modifier. Inputs relative to the heated backlight system 224 status (on/off) may be used by the controller 228 to calculate a Heated Rear Glass Modifier. Inputs relative to a heated windshield 218 status (on/off) may be used by the controller 228 to calculate a Heated Windshield Modifier. As will be appreciated, the described Modifiers represent (in percentage form, i.e. 0-100%) a relative contribution of each of the above inputs/vehicle systems to the overall probability of window fogging.

The controller 228 could of course calculate the above-described fogging probability and Modifiers in real or near-real time according to suitable algorithms. Alternatively, the controller 228 may compare the above-described inputs to one or more stored look-up tables (see FIG. 5), which of course may be stored by the controller 228 or in other suitable storage of another controller. In one possible embodiment, the inputs from the windshield humidity sensor 234 (measured in %) and the ambient temperature sensor 236, and optionally the calculated rate of change of humidity over time, are compared to stored values of a look-up table A to determine an initial probability of fogging. In turn, the blower 208 motor speed/HVAC system 202 airflow distribution mode inputs, the vehicle occupancy sensor 235 inputs, the windshield wiper system 222 status inputs, the heated windshield 218 status inputs, and the heated backlight system 224 status inputs are compared against the same or different stored look-up tables B, C, D, E, and F to determine Modifiers as described above. The Modifiers are combined with the original estimate of fogging probability to refine that original estimate, and to provide a refined fogging probability prediction 406 as a percentage (from 0-100%).

All such modifications and variations are within the scope of the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled. 

What is claimed:
 1. A method for defogging a window of a vehicle, comprising: determining a risk of window fogging; and automatically selecting a climate control system operating mode according to the determined risk of window fogging from the group consisting of: an outside air mode, an air-conditioning mode, and a defrost mode.
 2. The method of claim 1, including determining the risk of window fogging by a controller according to one or more inputs.
 3. The method of claim 2, including automatically selecting the climate control system operating mode by the same or a different controller.
 4. The method of claim 3, including, by the controller or the different controller, selecting a one of the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging.
 5. The method of claim 3, including, by the controller or the different controller, sequentially actuating the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging.
 6. The method of claim 4, including, by the controller or the different controller according to the determined risk of window fogging, increasing a climate control system blower speed to increase a rate of airflow provided by the selected one of the outside air mode, the air-conditioning mode, and the defrost mode.
 7. The method of claim 5, including providing intervening steps of, by the controller or the different controller according to the determined risk of window fogging, increasing a climate control system blower speed to increase a rate of airflow provided by one or more of the outside air mode, the air-conditioning mode, and the defrost mode.
 8. The method of claim 2, including providing the one or more inputs to the controller respectively by the group consisting of a windscreen relative humidity sensor, a vehicle-associated exterior ambient temperature sensor, a passenger cabin temperature sensor, a window wiper system mode sensor, and a window heated glass mode sensor.
 9. The method of claim 3, including providing the controller and/or the different controller comprising one or more processors associated with a vehicle climate control module (CCM).
 10. A method for defogging a window of a vehicle, comprising: providing one or more inputs to a processor comprised in a vehicle climate control module (CCM); by the processor, determining a risk of window fogging according to the one or more inputs; and by the same or a different processor, automatically selecting a climate control system operating mode according to the determined risk of window fogging from the group consisting of: an outside air mode, an air-conditioning mode, and a defrost mode.
 11. The method of claim 10, including, by the processor or the different processor, selecting a one of the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging.
 12. The method of claim 10, including, by the processor or the different processor, sequentially actuating the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging.
 13. The method of claim 11, including providing intervening steps of, by the processor or the different processor, increasing a climate control system blower speed to increase a rate of airflow provided by one or more of the outside air mode, the air-conditioning mode, and the defrost mode.
 14. The method of claim 12, including providing intervening steps of, by the processor or the different processor, increasing a climate control system blower speed to increase a rate of airflow provided by one or more of the outside air mode, the air-conditioning mode, and the defrost mode.
 15. The method of claim 10, including providing the one or more inputs to the processor by the group of sensors consisting of a windscreen relative humidity sensor, a vehicle-associated exterior ambient temperature sensor, a passenger cabin temperature sensor, a window wiper system mode sensor, and a window heated glass mode sensor.
 16. A window defogging system for a vehicle, comprising: one or more processors comprised in a vehicle climate control module (CCM) and configured to determine a risk of window fogging according to one or more received inputs; one or more sensors adapted to send the one or more inputs to the one or more processors; and a climate control system operatively connected to the one or more processors; wherein the one or more processors are further configured to actuate the climate control system in one or more of an outside air mode, an air-conditioning mode, and a defrost mode according to the determined risk of window fogging.
 17. The window defogging system of claim 16, wherein the one or more processors are configured to select a one of the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging or to sequentially actuate the outside air mode, the air-conditioning mode, and the defrost mode according to the determined risk of window fogging.
 18. The window defogging system of claim 17, wherein the one or more processors are further configured to increase a climate control system blower speed to increase a rate of airflow provided in one or more of the outside air mode, the air-conditioning mode, and the defrost mode before advancing to a next climate control system window defog system operating mode.
 19. The window defogging system of claim 17, wherein the one or more sensors are selected from the group consisting of a windscreen relative humidity sensor, a vehicle-associated exterior ambient temperature sensor, a passenger cabin temperature sensor, a window wiper system mode sensor, and a window heated glass mode sensor. 